This study demonstrates that Streptomyces spitsbergensis, described as a new species in 1993, is actually identical to the previously described Streptomyces baldaccii. Researchers obtained strains from culture collections and performed detailed morphological, cultural, and physiological characterization using standardized International Streptomyces Project methods. Both organisms exhibited verticillate (whorl-forming) aerial mycelia with red coloration, utilized only glucose and inositol as carbon sources, and produced melanin on specific media. DNA-DNA hybridization experiments revealed 86-93% relatedness between the two strains, well above the threshold for species identity. The researchers also confirmed findings that several other whorl-forming red Streptomyces species (S. roseoverticillatus, S. biverticillatus, S. fervens) share >80% DNA relatedness with S. baldaccii, making them synonymous. Based on these molecular and phenotypic data, the authors propose that S. spitsbergensis is a later subjective synonym of S. baldaccii, with the older name taking precedence in bacterial nomenclature.

Key findings

• S. spitsbergensis forms verticillate aerial mycelia, contradicting original descriptions of recti-flexibilis morphology
• DNA-DNA hybridization shows 86-93% relatedness between S. spitsbergensis and S. baldaccii, indicating they are the same species
• Morphological, cultural, and physiological characteristics of both strains are nearly identical, including carbon source utilization patterns
• S. spitsbergensis is designated a later subjective synonym of S. baldaccii, with the latter name retained according to nomenclatural rules